The present invention relates to a master tubular key which locks and unlocks a group of different keys and a combination tubular lock and master key therefor after.
Generally, referring to FIG. 3, a conventional lock for co-operating with a conventional tubular key (not shown) has a tubular lock case 70 fixed to a door or the like (not shown) and a tumbler enclosed by the lock case 70. The lock case 70 has an outward-facing opening. The tumbler consists of a first section 75, formed integral with a central portion 74, and a second section 76.
The first section has substantially a configuration of a column with a first end for restraining a tubular key in working position, a second end for rotating a bolt (not shown), and an enlarged portion between the ends. The enlarged portion of the first section 75 has a group of first tunnels extending therethrough parallel to a length of the first section 75. A first group of pins 71 is received in the first group of tunnels. In length, the first pins 71 are different from each other and are greater than the first tunnels. The first section 75 is received in the lock case 70 with the first end thereof in the opening of the tubular lock case, thereby forming an annular key hole.
The second section 76 has a configuration of a sleeve defining a central hole and a second group of tunnels each corresponding to one of the first group of tunnels and extending for the same distance therein, thereby forming a bottom. A group of identical springs 73 are each received in one of the second group of tunnels. A second group of pins 72 in which the pins are equal to each other in length and are each received in one of the second group of tunnels.
The second section 76 is fixed in the lock case 70 with the second end of the first section extending through the central hole thereof. The second group of tunnels is aligned with the first group of tunnels, so that each second pin 72 is urged partially into one of the first group of tunnels by a spring 73, thereby preventing the first section 75 from rotating relative to the second section 76.
A conventional tubular key has a tubular body having an outer periphery defining a group of channels corresponding to the first group of pins 71 and extending parallel to a length thereof. Each channel has a length corresponding to that of one of the first group of pins 71, so that a length of one of the first pins 71 minus a length of one of the channels is equal to a length of another of the first pins 71 minus a length of another of the channels. When the tubular key is inserted in the key hole, the first pins 71 are, at first ends thereof, each received in a channel of the tubular key, so that they are co-planar at second ends thereof. The first pins 71 in turn urge the second pins 72 back into the second tunnels while the first pins 71 remain in the first tunnels, thereby allowing the first section 75 to rotate relative to the second section 76.
Such locks and keys are usually employed in personal computers or video games for commercial use in casinos. Generally, a big office has many personal computers each having a unique lock co-operating with a unique key, which is kept by a clerk. A clerk might lock a personal computer and leave the office with the key. If the clerk is absent from the office, a colleague cannot retrieve data from the personal computer without the clerk, because the personal computer is not accessible without the key. To solve such problem, a number of spare keys must be stored in the office. In a casino, there are many video games each having a unique lock co-operating with a unique key. A casino keeper needs to store a number of keys in order to access every video game to retrieve coins therefrom. Both instances are not convenient. Therefore, the present invention is intended to solve this problem.